1. Field of the Invention
The present invention relates to a fabricating method of an organic electro luminescence display device and an organic electro luminescence display device using the same, and more particularly to a fabricating method of an organic electro luminescence display device that simplifies its manufacturing process by forming a barrier rib by use of a new material, and an organic electro luminescence display device using the same.
2. Discussion of the Related Art
Recently, various flat panel display devices have been developed that have reduced weight and bulk to overcome the disadvantages of a cathode ray tube (CRT). Such flat panel display devices include a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (hereinafter, referred to as ‘PDP’) and an organic electro luminescence (hereinafter, referred to as ‘EL’) display, etc.
Among them the PDP is simple in structure and fabrication process, thus the PDP is drawing attention as the most advantageous display device to be made in large sizes while being light and thin but there is a disadvantage in that its light emission efficiency and brightness are low and its power consumption is high. In comparison to this, an active matrix LCD having a thin film transistor (hereinafter, referred to as ‘TFT’) as a switching device uses a semiconductor process, thus it is difficult to make large LCDs due to manufacturing yield problems, and its power consumption is high due to a backlight unit. Further, the LCD has a disadvantage in that its viewing angle is narrow and there is a high light loss by optical devices such as a polarizing filter, a prism sheet, a diffusion plate, etc.
In comparison to this, the EL display device is generally divided into an inorganic EL display device and an organic EL display device in accordance with the type of material in a light emitting layer. The EL display is a self luminous device and has an advantage in that its response speed is fast, its light emission efficiency and brightness are high and its viewing angle is wide. An inorganic EL display device has higher power consumption than an organic EL display device, and the inorganic EL display device does not have high brightness and does not emit light with various colors of R (red), G (green) and B (blue). On the contrary, the organic EL display device is driven at a low DC voltage of several tens of volts, and the organic EL display device has a rapid response speed, has high brightness and can emit light with various colors of R, G, B, thus it is suitable for the next generation flat panel display device.
The organic EL display device includes sub-pixels arranged in an area defined by the crossing of gate lines and the data lines. The sub-pixel receives a data signal from the data line when a gate pulse is supplied to the gate line, and the sub-pixel emits light corresponding to the data signal, thereby displaying a picture.
The organic EL display device includes: an upper array substrate where an EL cell is formed; a lower array substrate where a drive TFT for driving the EL cell is formed; and a spacer that connects a cathode electrode of the EL cell to a drain electrode of the drive TFT.
Currently, the EL cell is formed to be separated by barrier ribs, and the barrier rib is formed in a reverse taper shape in order to divide the EL cell. The barrier ribs of the reverse taper shape effectively divide an organic light emitting layer of the EL cell and further make the cathode electrode separated by only the deposition of an electrode material without patterning. Accordingly, its yield is improved because the organic EL display device effectively separates the organic light emitting layer by the barrier ribs with the reverse taper shape, and its manufacturing cost is reduced because the cathode electrode is formed without being patterned.
Hereinafter, in reference to FIGS. 1A to 1C, a detailed description will be made for a method of forming the barrier ribs with the reverse taper shape of the organic EL display device as follows.
Referring to FIG. 1A, according to a fabricating method of a barrier rib 8 with a reverse taper shape in an organic EL display device of the related art, a silicon nitride SiN×1 8a is deposited on the entire surface of an upper substrate 2, where a bus electrode 5, an anode electrode 4 and an insulating film 6 are formed, at a temperature of not greater than 280° C.
Subsequently, a silicon nitride SiN×2 8b is deposited on the entire surface of the silicon nitride SiN×1 8a that is deposited on the entire surface at a temperature of not greater than 280° C., at a temperature greater than 350° C., as shown in FIG. 1B. And then, the silicon nitride 8a, 8b is patterned by a photolithography process and a dry etching process, thereby forming the barrier rib 8 with an upright taper in a lower part and a reverse taper in an upper part, as shown in FIG. 1C.
Herein, the silicon nitride has a characteristic of being differently etched during the dry etching process in accordance with the deposit temperature. To describe this in detail, the silicon nitride deposited at the temperature of not greater than 280° C. is etched with an upright taper shape by the dry etching process, and the silicon nitride deposited at the temperature greater than 350° C. is etched in the reverse taper shape by the dry etching process. Accordingly, the barrier rib 8 of the organic EL display device of the related art deposits the silicon nitride at different temperatures, and thus, by use of the characteristic of the silicon nitride it is possible to form the barrier rib 8 having an upright taper shape in the lower part and the reverse taper shape in the upper part.
However, the fabricating method of the organic EL display device of the related art has a characteristic that the silicon nitride SiN×2 deposited at the temperature greater than 350° C. is etched to have a large reverse taper, as shown in FIG. 2, by the dry etching process. Due to this, the fabricating method of the organic EL display device of the related art produces a phenomenon where an area where the organic light emitting layer 10 can be formed is hidden by the big reverse taper and should form the barrier rib 8 with a height higher than a height by which the organic light emitting layer 10 is filled.
Accordingly, the fabricating method of the organic EL display device of the related art lowers the thickness of the silicon nitride deposited at the temperature greater than 350° C. in order to reduce the height of the barrier rib SiN×2 8b with the reverse taper shape, thereby reducing the phenomenon that the area where the organic light emitting layer 10 can be formed is hidden by the barrier rib 8b with the reverse taper shape. The fabricating method forms the barrier rib 8a with the upright taper by depositing the silicon nitride at the temperature of not greater than 280° C. in the lower part of the barrier rib 8b with the reverse taper, thereby forming the barrier rib 8 at the height by which the organic light emitting layer 10 can be filled.
Accordingly, the fabricating method of the organic EL display device of the related art deposits an inorganic material such as the silicon nitride at deposition temperatures that are different from each other, thus the barrier rib 8a with the upright taper shape is formed at the lower part and the barrier rib 8b with the reverse taper shape is formed at the upper part, thus there is a disadvantage that the number of processes for forming the barrier rib 8 with the reverse taper shape is increased because the barrier rib 8 is formed in double layer.
Also, according to the related art, if the silicon nitride deposited on a substrate in single layer, for example, at the temperature greater than 350° C., then patterned by a dry etching process to form a barrier rib, the barrier rib is formed in an upright taper by the characteristic of the dry etching process. So, according to the related art, a barrier rib with a reverse taper can not be achieved in single layer using a silicon nitride.
According to another related art, a barrier rib can be formed by depositing photosensitive organic material on a substrate and pattering it with a photolithography process. However, as the barrier rib formed by organic material is easily contaminated, therefore it decreases processing yield and causes a break in electrodes of an organic electro luminescence display frequently.